Now, I'm not really interested in yet another 6d vs 5d3 debate, but it's hard not to reply :-p ... but I'll try to let this be my last comment on this specific issue.
Is it logical to just take a camera based on your needs ... Again, if you think 6D isn't the "best" for you then why choose it?
Oh my, that's good ol' CR "Just get a 1dx, 70-200L2, 24-70L2 and be done with it" :-> ... I'm rather amazed about these questions, but fyi I can think of 1200 reasons with an € label attached :-o
You said "it's the complete package that counts". Now, that's not being logical.
On the contrary, though I admit this was not very precise. I define "complete package" as Canon marketing and statistics would define it, i.e. what what user groups willing how many $$$ to spend need... and then they do or modify the specs.
Imho there is a rather linear "complete package" scale, Rebel "shoot your family on birthdays" group have different needs than the enthusiasts around here. For example looking at the posts, users who buy a ff also want some sort of sealing and pref. a 100% vf - so Canon uses these pieces of information to assemble packages like "6d good sensor / lacking sealing / cropped vf" and "5d3 has it all". These are just examples from the top of my head, but you get the picture.
5d3 vs 6d is a tough choice for me, if I were given either to use regularly for free and could not sell I'm not sure what I would pick.
For me it wasn't because I'm $$$ limited and bodies loose their price much quicker than lenses. I keep commenting on the 6d's af shortcomings as I'm annoyed Canon crippled it beyond what would have been required to separate if from the 5d3.
But truth is, *if* the shot is in focus (and that's not difficult with landscape and such) it has terrific iq and significantly less banding than the 5d3, and at the end of the day people aren't interested in how many shots were lost but only how good the one shot left is. So if I don't lose the shot of my life because the 6d's af fails I'd rather spend the 6d->5d3 difference on lenses, because that's what you see (through).